Manifold imaging method wherein the activator carries a plastic coating material

ABSTRACT

An imaging system wherein a structure comprising a cohesively weak imaging layer sandwiched between a donor sheet and a receiver sheet is used. The imaging layer is activated with an activator comprising at least two components, one of the components being a plastic, the other being a partial solvent for the imaging layer. Upon separation of the receiver and donor sheets a durable, workable, plastic surface is obtained on the image. This surface may then be buffed providing a transparency which will project a true color image.

[ 51 Mar. 27, 1973 [54] MANIFOLD IMAGING METHOD WHEREIN TIIE ACTIVATOR CARRIES A PLASTIC COATING MATERIAL [75] Inventor: Ray 11. Luebbe, Jr., Rochester, N.Y.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: July 10, 1970 [21] Appl. No.: 53,750

Related U.S. Application Data [63] Continuation-impart of Ser. No. 675,989, Oct. 17,

1967, abandoned.

[52] U.S. Cl ..96/l.2, 96/1 R, 96/l.3, 96/1.4, 96/l.5 [51] Int. Cl. ..G03g 13/22, 603g 5/06 [58] Field of Search ..96/1 LX, 1.3, l.4,1.2,1; 117/37 LE [56] References Cited UNITED STATES PATENTS 3,598,581 8/1971 Reinis ..96/l R 3,512,968 5/1970 Tulagin ..96/l X 3,520,681 7/1970 Goffe 3,574,614 4/l97l Carreira ..1 17/37 LE Primary Examiner-George F. Lesmes Assistant Examiner-Roland E. Martin, Jr. Attorney-James .1. Ralabate, David C. Petre and Raymond C. Loyer [57] ABSTRACT An imaging system wherein a structure comprising a cohesively weak imaging layer sandwiched between a donor sheet and a receiver sheet is used. The imaging layer is activated with an activator comprising at least two components, one of the components being a plastic, the other being a partial solvent for the imaging layer. Upon separation of the receiver and donor sheets a durable, workable, plastic surface is obtained on the image. This surface may then be buffed providing a transparency which will project a true color image.

13 Claims, 5 Drawing Figures PATENTEUMmmn 3,723,112

9 I KKKKKKKKKKKKKKKKK q FIG.

FIG. IA

ACTIVATE SANDWICH FIG. 2

APPLY FIELD AND EXPOSE 1 SEPARATE INVENTOR. Fl 4 RAY HLUEBBE JR.

FIG. 3 BY ATTORNEY MANIFOLD IMAGING METHOD WHEREIN THE ACTIVATOR CARRIES A PLASTIC COATING MATERIAL BACKGROUND OF THE INVENTION This application is a continuation-in-part of commonly assigned, copending application Ser. No. 675,989 filed Oct. 17, 1967, now abandoned. The present invention relates in general to imaging and more specifically to a system for the formation of images by layer transfer in image configuration.

Although imaging techniques based on layer transfer of a colored material have been known in the past, these techniques have always been clumsy and difficult to operate because they depend upon photochemical reactions and generally involve the use of distinct layer materials for the two functions of imagewise transfer and image coloration. A typical example of the complex structures and sensitive materials employed in prior art techniques is described in US. Pat. No. 3,091,529 to Buskes. A more comprehensive discussion of prior art imaging techniques based on layer transfer may be found in copending application Ser. No. 708,380 filed Feb. 26, 1968 in the U. S. Patent ffice which is incorporated herein by reference.

Copending application Ser. No. 708,380 describes an imaging system utilizing a manifold set comprising a photo-responsive material between a pair of sheets. In this imaging system an imageable plate is prepared by coating a layer of a cohesively weak photoresponsive imaging material onto a substrate sheet. This coated sheet is called the donor. In preparation for the imaging operation the imaging layer is activated as by treating it with a swelling agent, softening agent, solvent or partial solvent for the material or by heating. This step may be eliminated, of course, if the layer retains sufficient residual solvent after having been coated on the substrate sheet from a solution or paste. The activating step serves to weaken the imaging layer structurally so that it can be fractured more easily along a sharp line which defines the image to be reproduced. Once the imaging layer is activated, a receiving sheet is laid down over its surface. An electrical field is then applied across this manifold set and the imaging layer is exposed to a pattern of light and shadow representative of the image to be reproduced. Upon separation of the donor sheet and receiving sheet, the imaging layer fractures along the lines defined by the pattern of light and shadow to which the imaging layer has been exposed, with part of this layer being transferred to the receiving sheet while the remainder is retained on the donor sheet so that a positive image, that is, a duplicate of the original is produced on one sheet while a negative image is produced on the other.

At least one of the donor sheet and the receiver sheet is at least partially transparent to permit exposure of the imaging material to the image to be reproduced. The imaging layer serves a dual function in imparting light sensitivity to the system while at the same time acting as colorant for the final image produced. In one form the imaging layer comprises a photosensitive material such as metal free phthalocyanine dispersed in a cohesively weak insulating binder. However, the images prepared in accordance with copending application Ser. No. 708,380 as described above have been found to be susceptible to smudging or scratching or handling. In addition, it has been found that when the system described above and in copending application Ser. No. 708,380 is used to prepare transparencies that the surface of the image is rough causing light scattering which in turn prevents the projection of a high quality colored image. As is disclosed in copending application Ser. No. 708,380, the images obtained after separating the donor and receiver sheets may be overcoated with a thermoplastic material to improve their handling quality, however, this requires an additional process step.

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide an imaging system which overcomes the above noted disadvantages.

It is another object of this invention to provide a layer transfer imaging system which provides comparatively durable images.

It is another object of this invention to provide a layer transfer imaging system which provides comparatively durable images and does not require a separate overcoating step.

It is another object of this invention to provide a layer transfer imaging system which provides a protective layer over the image which may be worked such as, for example, by buffing.

It is another object of this invention to provide a system for layer transfer imaging which provides transparencies which project relatively high quality color images.

It is another object of this invention to provide a system for layer transfer imaging which provides a surface which may be treated to substantially prevent surface light scattering.

The above objects and others are accomplished in accordance with this invention by an imaging system utilizing a structure comprising a structurally weak imaging layer sandwiched between a donor sheet and a receiving sheet. The imaging layer has initially a stronger degree of adhesion for the donor sheet than for the receiver sheet. The imaging layer is activated by brushing a two component activator on its surface. The activator comprises a liquid which is a solvent, partial solvent, softening agent or swelling agent collectively referred to herein after as solvent component and at least one plastic component. The plastic component may be dispersed, suspended or dissolved in the liquid component of the activator. After activation the donor sheet imaging layer and receiver sheet are placed together. Alternatively, the activator may be placed on the surface of the receiver sheet. A charge is placed across the imaging layer and the imaging layer is exposed to light projected from an image to be reproduced. After imaging, the donor sheet and receiver sheet are separated providing a positive image, that is, a duplicate of the original on one of said receiver or donor sheets and a negative image on the other sheet. The volatile component of the activator evaporates in air leaving behind a coating of the plastic component of the activator on at least one of the images. Since the best quality images are produced by exposing through the donor substrate, it is preferred to use the image adhering to the donor sheet as the final product. The image adhering to the donor sheet may be either a positive or a negative image.

The activator may be supplied in the form of a low melting point solid, which on heating serves to activate the imaging layer, see for example, copending application Ser. No. 628,028, filed Apr. 3, 1967 in the U. S. Patent Office, now U. S. Pat. No. 3,598,581, which is incorporated herein by reference. in such a system, the activating layer comprises a material which melts at a lower temperature than the imaging layer upon heating and renders it weak structurally so that it can be fractured while under an electric field along a sharp line which defines the exposure to electromagnetic radiation to which the imaging layer is sensitive. Thus, after exposure when the receiver sheet is stripped from the imaging material, portions of the imaging material transfer to the receiver sheet in image configuration while the remainder is retained on the substrate so that a positive image is produced on one while a negative image is produced on the other. The body of the imaging layer and activating layer may be at ambient temperatures structurally strong thus capable of withstanding shipping and storage. Only when activated by the application of heat does the imaging layer become structurally fracturable in response to an electric field and exposure to electromagnetic radiation to which the layer is sensitive.

Preferably, the solvent component of the activator acts as a solvent for the plastic component of the activator as well as a partial solvent, that is, a softening or weakening agent, for the imaging layer so that on evaporation of the solvent component of the activator the plastic component is bonded thoroughly to the image. It is also possible to provide a donor sheet and/or receiver sheet which is softened by the partial solvent which would provide increased adhesion between the coated image and the donor and/or receiver sheet upon evaporation of the partial solvent component.

In the preferred embodiment of this invention wherein the solvent component acts as a solvent for the plastic component and a partial solvent for the imaging layer the activator solution will penetrate the imaging layer to a degree depending on how much activator is used, the temperature of the system and the length of time that the imaging layer is exposed to the partial solvent. At one extreme, therefore, upon evaporation of the partial solvent component the plastic component of the activator would be dispersed evenly throughout the imaging layer, whereas at the opposite extreme the plastic component would form a distinct overcoating layer on the surface of the imaging layer. It should be understood, therefore, that for the purposes of this disclosure that the term overcoating is meant to include layers which penetrate and become intimately dispersed within the final image as well as distinct overcoating layers.

The light image may be formed by passing light through a transparency or by projecting light information from an opaque subject.

The manifold set may include separate electrodes on opposite sides of the donor substrate and receiver sheet for the application of the field or they may be directly on the back surfaces of these members and integral therewith, or one or both of the donor substrate and receiver sheet may be made of a conductive material. The donor substrate and the receiving sheet may consist of the same or different materials. Any suitable conductive material may be used for these sheets such as cellophane. Alternatively, the donor substrate and the receiving sheet may consist of any suitable electrically insulating or conducting material. Typical insulating materials include polyethylene; polypropylene; polyethylene terephthalate; polystyrene; cellulose acetate; celluloseacetate butyrate; paper; plastic coated paper, such as, polyethylene coated paper and mixtures thereof. Mylar, a polyester formed by the condensation reaction between ethylene glycol and terephthalic acid, available from the E. l. duPont de Nemours Co., lnc., is preferred because of its physical strength and because it has good insulating qualities. Conductive materials such as aluminum foil, impregnated plastics and other metalic sheet materials can also be employed.

Where the manifold set is made up of an insulating receiver sheet and an insulating donor sheet, charging may be accomplished prior to imaging by using corona discharge devices such as those described in U.S. Pat. No. 2,588,699 to Carlson, U.S. Pat. No. 2,777,957 to Walkup, U.S. Pat. No. 2,885,556 to Gundlach, or by using conductive rollers as described in U.S. Pat. No. 2,980,834 to Tregay et al., or by frictional means as described in U.S. Pat. No. 2,297,69l to Carlson, or other suitable apparatus. The electrodes may consist of any suitable conductive material. Typical conductive electrode materials include aluminum, brass, stainless steel, copper, nickel, zinc and mixtures thereof. Aluminum is preferred because it is readily available and because it is a good conductor.

Where it is desired to charge simultaneously with imagewise exposure, any suitable transparent conductive electrode material may be used. Typical conductive transparent electrode materials include conductively coated glass such as tin or indium oxide coated glass; aluminum coated glass; or similar coatings on plastic substrates. NESA, a tin oxide coated glass available from the Pittsburgh Plate Glass Co., is preferred because of its high transparency.

The solvent component of the activator may consist of any suitable volatile or non-volatile solvent. Typical solvent materials include kerosene; carbon tetrachloride; petroleum ether; silicone oils; such as dimethyl-polysiloxanes; long chain aliphatic hydrocarbon oils such as those ordinarily used as transformer oils; trichloroethylene, chlorobenzene; benzene toluene; xylene, hexane; acetone; vegetable oils; and mixtures thereof.

The plastic component of the activator may comprise any suitable thermoplastic or thermosetting materials. Typical materials include polyethylene; polypropylene; polybutylene; polyamides; polymethacrylates; polyacrylates; polyvinyl chlorides; polyvinylacetates; polystyrene; polysiloxanes; chlorinated rubbers; polyacrylonitrile; polyurethanes; epoxies; phenolics; chlorinated polyphenols; hydrocarbon resins and other natural resins such as rosin derivatives; waxes, such as paraffinic and microcrystalline waxes, as well as mixtures and copolymers thereof. Piccotex 120, (a styrene-vinyl toluene copolymer), available from the Pennsylvania Industrial Chemical Co., is preferred because it forms a durable, workable surface on the image.

The imaging layer may comprise any suitable photoresponsive material in a binder. Typical photoresponsive materials include photoconductors such as those disclosed in copending application Ser. No. 708,380. Phthalocyanines are preferred because of their high sensitivity and excellent color. Of the phthalocyanines alpha and X forms of metal-free phthalocyanines have given optimum results. However, any other suitable phthalocyanine may be used where desired.

Any suitable phthalocyanine may be used to prepare the photoconductive layer of the present invention. The phthalocyanine used may be in any suitable crystal form. It may be substituted or unsubstituted both in the ring and straight chain portions. Reference is made to a book entitled Phthalocyanine Compounds by F. H. Moser and A. L. Thomas, published by the Reinhold Publishing Co., 1963 edition for a detailed description of phthalocyanines and their synthesis. Phthalocyanines may be described as compositions having four isoindole groups linked by four nitrogen atoms in such a manner so as to form a conjugated chain, said compositions have the general formula (C l-l,N R, wherein R is selected from the group consisting of hydrogen, deuterium, lithium, sodium, potassium, copper, silver, beryllium, magnesium, calcium, zinc, cadmium, barium, mercury, aluminum, gallium, indium, lanthanum, neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium, thulium, ytterbium lutecium, titanium, tin, hafnium, lead, silicon, gervanium, thorium, vanadium, antimony, chromium, molybdenum, uranium, manganese, iron, cobalt, nickel, rhodium, palladium, osmium, and platinum, and n is a value of greater than 0 and equal to or less than 2. Any other suitable phthalocyanines such as ring or aliphatically substituted metallic and/or non-metallic phthalocyanines may also be used if suitable. Typical of these phthalocyanines are: aluminum phthalocyanine, aluminum polychlorophthalocyanine, antimony phthalocyanine, barium phthalocyanine, beryllium phthalocyanine, cadmium hexadecachlorophthalocyanine, cadmium phthalocyanine, calcium phthalocyanine, cerium phthalocyanine, chromium phthalocyanine, cobalt phthalocyanine, cobalt chlorophthalocyanine, copper aminophthalocyanine, copper bromochlorophthalocyanine, copper 4-chlorophthalocyanine, copper 4-nitrophthalocyanine, copper phthalocyanine, copper phthalocyanine sulfonate, copper polychlorophthalocyanine, deuteriophthalocyanine, dysprosium phthalocyanine, erbium phthalocyanine, europium phthalocyanine, gadolinium phthalocyanine, gallium phthalocyanine, germanium phthalocyanine, hafnium phthalocyanine, halogen substituted phthalocyanine, holmium phthalocyanine, indium phthalocyanine, iron phthalocyanine, iron polyhalophthalocyanine, lanthanum phthalocyanine, lead phthalocyanine, lead polychlorophthalocyanine, cobalt hexaphenylphthalocyanine, copper pentaphenylphthalocyanine, lithium phthalocyanine, lutecium phthalocyanine, magnesium phthalocyanine, cyanine, manganese phthalocyanine, mercury phthalocyanine, molybdenum phthalocyanine, naphthalocyanine, neodymium phthalocyanine, nickel phthalocyanine,

nickel polyhalophthalocyanine, osmium phthalocyanine, palldium phthalocyanine, palladium chlorophthalocyanine,. alkoxyphthalocyanine, al-

kylaminophthalocyanine, alkylmercaptophthalocyanine, aralkylaminophthalocyanine, aryloxyphthalocyanine, arylmercaptophthalocyanine, copper phthalocyanine piperidine, cycloalkylaminophthalocyanine, dialkylaminophthalocyanine, diaralkylaminophthalocyanine, dicycloalkylaminophthalocyanine, hexadecahydrophthalocyanine, imidomethylphthalo cyanine, 1,2 naphthalocyanine, 2,3 naphthalocyanine, octaazaphthalocyanine, sulfur phthalocyanine, tetraazaphthalocyanine, tetra-4-acetylaminophthalocyanine, tetra-4-aminobenzoylphthalocyanine, tetra-4- aminophthalocyanine, tetrachloromethylphthalocyanine, tetradiazophthalocyanine, tetra-4,4- dimethyloctaazaphthalocyanine, tetra-4,5-diphenylenedioxide phthalocyanine, tetra-4,5-diphenyloctaazaphthalocyanine, tetra-(6 methyl-benzothiazoyl) phthalocyanine, tetra-p-methylphenylaminophthalocyanine, tetra-methylphthalocyanine, tetranapthotriazolylphthalocyanine, tetra-4- naphthylphthalocyanine, tetra-4-nitrophthalocyanine, tetra-perinaphthylene-4,5-acta-azaphthalocyanine, tetra-2,3-phenyleneoxide phthalocyanine, tetra-4- phenyloctaazaphthanlocyanine, tetraphenylphthalocyanine, tetraphenylphthalocyanine tetracarboxylic acid, tetraphenylphthalocyanine tetrabarium carboxylate, tetraphenylphthalocyanine tetra-calcium carboxylate, tetrapyridyphthalocyanine, tetra-4- trifluoromethylmercaptophthalocyanine, tetra-4- trifluoromethylphthalocyanine, 4,5-thionaphthene-octaazaphthalocyanine, platinum phthalocyanine, potassium phthalocyanine, rhodium phthalocyanine, samarium phthalocyanine, silver phthalocyanine, silicone phthalocyanine, sodium phthalocyanine, sulfonated phthalocyanine, thorium phthalocyanine, thulium phthalocyanine, tin chlorophthalocyanine, tin phthalocyanine, titanium phthalocyanine, uranium phthalocyanine, vanadium phthalocyanine, ytterbium phthalocyanine, zinc chlorophthalocyanine, zinc phthalocyanine, others described in the Moser test and mixtures, dimers, trimers, digomers, polymers, copolymers or mixtures thereof.

It is also to be understood that the photoconductive particles themselves may consist of any suitable one or more of the aforementioned photoconductors, either organic or inorganic, dispersed in, in solid solution in, or copolymerized with, any suitable insulating resin whether or not the resin itself is photoconductive. This particular type of particle may be particularly desirable to facilitate dispersion of the particle, to prevent undesirable reactions between the binder and the photoconductor or between the photoconductor and the activator and for similar purposes. Typical resins include polyethylene, polypropylene, polyamides, polymethacrylates, polyacrylates, polyvinyl chlorides, polyvinyl acetates, polystyrene, polysiloxanes,

chlorinated rubbers, polyacrylonitrile, epoxies, phenolics hydrocarbon resins and other natural resins such as rosin derivatives as well as mixtures and copolymers thereof. Polyethylene is preferred because of its low melting point.

The binder material in the heterogeneous imaging layer may comprise any suitable cohesively weak insulating or photoconductive insulating materials. Typical cohesively weak materials include the insulating resins listed above particularly the lower molecular weight polyethylenes and polypropylenes; vinyl ethylene copolymers; styrene-vinyl toluene copolymers; microcrystalline wax; paraffin wax; other low molecular weight polymers and copolymers and mixtures thereof.

In the heterogeneous system, the ratio of photoconductor to binder in photoresponsive layer 12 may range from about 10:1 to about 1:10 (by volume), but it has generally been found that proportions in the range from about 1:2 to about 2:1 produce the best results and, accordingly, this constitutes a preferred range.

A mixture of microcrystalline wax, styrene-vinyl toluene copolymers, low molecular weight polyethylene and vinylacetate ethylene copolymer is preferred because it is a good insulator.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages of this improved method of imaging will become apparent upon consideration of the detailed disclosure of the invention especially when taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a side sectional view of a photosensitive imaging member for use in this invention.

FIG. 1A is a side sectional view of a second embodiment of an imaging member of this invention.

FIG. 2 is a side sectional view diagrammatically illustrating the first two process steps of this invention.

FIG. 3 is a side sectional view diagrammatically illustrating the final two process steps of this invention.

FIG. 4 is a process flow diagram of the method steps of this invention.

Referring now to FIG. 1, imaging layer 6 comprising photosensitive particles 7 dispersed in binder 8 is deposited on insulating donor substrate sheet 5. The image receiving portion of the manifold set comprises insulating receiver sheet 9. Either or both sheets or 9 may be transparent so as to permit exposure of imaging layer 6. The embodiment of the invention shown in FIG. 1 is preferred because it allows for the use of high strength insulating polymeric materials as donor sheet 5 and receiver sheet 9.

Referring now to FIG. 1A of the drawings, there is seen a supporting substrate layer 11 and an imaging layer generally designated 10. Superimposed on imaging layer 10 is a receiving sheet 13. Imaging layer 10 is made up of electrically photosensitive layer coated on donor substrate 11 and activating layer 14 coated on photosensitive layer 15. Layer 12 is normally coated on substrate 11 so that it adheres thereto. Receiving sheet 13 is in contact with activating layer 14 but does not adhere strongly thereto. At ambient temperatures, imaging layer 10 is sufficiently cohesively strong as to permit reasonable handling, shipping and storage. However, layer 10 is capable of being rendered structurally fracturable upon heating. In the particular illustrative examples shown in FIG. 1A, imaging layer 10 consists of photoconductive pigment particles dispersed in a binder. This two-phase system has been found to constitute a preferred form for imaging layer 10 in that it gives images of good resolution and is highly photo-sensitive. However, homogeneous layers made up, for example, of a single component or a solid solution of two or more components may be employed where these materials exhibit the desired phoacetate- 7 toresponse and have the desired physical properties. Since imaging layer 10 serves as a photoresponsive element of the system as well as the colorant in the final image produced, the components of this layer are in most cases preferably selected so as to have a high level of photosensitivity while, at the same time, being intensely colored so that a high contrast image can be formed by the process of the invention. However, since the binder itself can be dyed or pigmented with additional colorant in either the single phase or two phase system, intense coloration of the photosensitive material itself, while being preferred, is not essential. Accordingly, the photosensitive material may be of any color, even transparent to visible light.

Activating layer 14 has a lower melting temperature than does imaging layer 10. Activating layer 14 may be homogeneous or heterogeneous; that is may include an activating material dispersed in a binder. During assembly of the manifold set, activating layer 14 may be formed initially either on the surface of imaging layer 10 or on the surface of receiving sheet 13. Activating layer 14 may comprise, alone or in a binder, a thermosolvent. A thermo-solvent is an ingredient which is solid at ordinary room temperatures but which melts slightly above room temperature. When melted, this material is a solvent, partial solvent, swelling agent or softening agent for imaging layer 10. By thus activating the imaging layer, it is rendered structurally fracturable in response to the combined effect of an electric field and exposure to electromagnetic radiation to which the layer is sensitive. Preferred thermosolvents are low melting waxes and include materials which are solid at room temperature but melt at temperatures below F. Especially good results have been obtained with long chain petroleum waxes with from about 18 to about 30 carbon atoms in the chain. Typical low melting waxes include octadecane, nonadecane, eicosane, heneicosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, heptacosane, octasocane, nonacosane, triacontane, and mixtures thereof. If desired, these low melting waxes and other thermosolvents may be mixed with other materials, such as higher melting waxes and binders which are soluble in the thermosolvent when the thermosolvent is melted. Typical thermosolvents which may be dispersed in a hinder or used alone where suitable include m-terphenyl, Aroclor 5442 (a chlorinated polyphenyl, melting point 4652 C. from Monsanto Chemical Company), perchloro hydrocarbons, polybutylenes, biphenyl and mixtures thereof. Typical binder materials suitable for use with some thermosolvents include the low melting waxes described above and the donor-layer binders listed above. Melting of the thermosolvent can be accomplished in many ways such as placing the imaging member on a heated platen or contacting it with hot air.

After imaging, separation of receiving sheet 13 from donor substrate 11 and cooling of the material to room temperature, the thermosolvent will resolidify. This will tend to fix images produced since the resin is now in a tougher, more abrasion resistant form. The images formed will be more easily handled and more resistant to abrasive damage.

Referring now to FIG. 2 which diagrammatically illustrates the alternative method of activating the imaging layer, FIG. 2 shows an activator fluid 23 being sprayed onto imaging layer 12 of the manifold set from container 24. Alternatively, the activator may be applied by any suitable techniques such as with a brush, with a smooth or rough surfaced roller, by flow coating, or the like. The activator serves to swell or otherwise weaken and thereby lower the cohesive strength of imaging layer 12. Electrode l7 and receiver sheet 16 are then lowered onto imaging layer 12 and roller 26 is rolled across the surface of electrode 17 to remove any excess activator fluid which may be present.

Referring now to FIG. 3, the manifold set is charged by connecting electrodes 17 and 18 to potential source 28 and resistor 30. The manifold set is then exposed to electromagnetic radiation 29 in image configuration. Receiver sheet 16 and donor sheet 19 are then separated. Upon separation imaging layer 12 fractures along the edges of exposed areas and at the surface where it had adhered to substrate 19. Accordingly, once separation is complete, exposed portions of imaging layer 12 are retained on one of layers 16 and 19 while unexposed portions are retained on the other layer. Although FIG. 3 shows a positive image being formed on the donor sheet, it is possible to form a negative image on the donor sheet. Once the partial solvent component of the activator has evaporated in air or by blowing hot air across the surface of the image, resinous film 21 is found formed on the surface of the image. Although the resinous film 21 is shown in FIG. 3 as a separate layer or stratum, it is likely that this resinous film penetrates through the imaging layer present as a uniform resinous film only at the very surface of the final image on the donor sheet particularly when the partial solvent component acts as a solvent for the plastic component.

When employing a particulate plastic component in the activator, an additional step of heating the surface of the image produced may be added. Such heating will serve to melt or soften the thermoplastic so that it will flow and thus cover the surface of the image. Alternatively, the particles can be flowed by pressing a heated plate or other smooth, non-adhering surface such as a roller on the surface of the image to spread the plastic over the surface.

DESCRIPTION OF PREFERRED EMBODIMENTS The following examples further specifically illustrate the present invention. The examples below are intended to illustrate various preferred embodiments of the improved imaging method. The parts and percentages are by weight unless otherwise indicated.

EXAMPLE I A commercial metal-free phthalocyanine is first purified by o-dichlorobenzene extraction to remove organic impurities. Since this extraction step yields the less sensitive beta crystalline form of phthalocyanine, the desired x form is obtained by dissolving approximately 100 grams of beta in approximately 600 cc. of sulfuric acid and precipitating by pouring the solution into about 3,000 cc. of ice water and washing with water to neutrality. The thus purified phthalocyanine is then salt milled for 6 days and desalted by slurrying distilled water, vacuum filtering, water washing and finally methanol washing until the initial filtrate is clear. After vacuum drying to remove residual methanol, the x form phthalocyanine is dispersed in a binder solution prepared as follows:

About 3 grams of polyethylene DYLT available from Union Carbide is purified by dissolving the DC Naphtha 2032 available from Standard Oil of Ohio, pouring with stirring into isoporpanol, filtering and drying. The purified polyethylene is added to about 1.5 grams of Paraflint R.G., a low molecular weight paraffinic material available from the Moore and Munger Co., New York City. About 0.5 grams of Elvax 420 available from E. I. duPont de Nemours & Co. purified in the same manner as the DYLT; and about 2.5 grams of Piccotex (a styrene-vinyl toluene copolymer available from the Pennsylvania Industrial Chemical Co.); and about 20 ml. of Sohio Odorless Solvent 3440 available from Standard Oil of Ohio are added to the DYLT and Paraflint. The mixture of binder materials is dissolved in the Sohio 3440 by heating and stirring. The solution is then allowed to cool to room temperature. The x form phthalocyanine is pre-milled with 60 ml DC Naphtha 2032 in a glass jar by revolving the glass jar containing glass balls at about 70 rpm for about 4 hours.

The binder solution prepared as above is then added to the pre-milled pigment-naphtha mixture and milling is continued for approximately 16 hours. The materials are then heated to a temperature of 65C for about 2 hours, and then are cooled to room temperature. About 60 ml of isopropanol is then added to the mixture and the mixture is milled as above for about 30 minutes. The mixture is then ready for coating on the donor substrate as follows:

A paste-like mixture is then coated in subdued green light on 3 mil Mylar (a polyester formed by the condensation reaction between ethylene glycol and terephthalic acid available from E. I. duPont de Nemours 8!. Co.) with a No. 36 wire wound drawdown wire to produce a coating thickness when dried of approximately 7 1% microns. The coating is then dried in the dark ata temperature of about 33C for about 5k hour. The coated donor is then placed on the tin oxide surface of a 1/16 inch thick NESA glass plate with its coating facing away from the tin oxide. A receiver sheet of 2 mil Mylar is placed over the donor. A sheet of black electrically conductive paper available as Grade 505 Black Photographic Paper from Knowlton Paper Co., Watertown, New York is placed over the receiver sheet.

An activator solution is prepared by dissolving enough Piccotex (a styrene-vinyl toluene copolymer available from the Pennsylvania Industrial Chemical Co.) in 500 cc. of Sohio 3440 to form a 20 percent solution.

A receiver sheet and black electrode are then lifted up and the imaging layer activated with a brush stroke of a wide camels hair brush saturated with the activator solution.

The receiver sheet and black electrode are then lowered back down and a roller is rolled slowly once over the closed manifold set with light pressure to remove excess solvent. The positive terminal of a 10,000 volt DC power supply is then connected to the NESA coating in series with a 500 megohm resistor and the negative terminal is connected to the black paper electrode and grounded. With the voltage applied, a

white incandescent light image is projected through the NESA glass using a 300 watt Bell and Howell Headliner Model 708 Duo Slide Projector having a piece of Trans-Positive Sheet (Frosted) available from Xerox and a variable aperture placed in front of it. The distance from the projector to the imaging donor layer is approximately 60 inches. The light incident on the imaging layer is adjusted to approximately I foot-candle. The imagewise exposure is continued for about 0.5 second resulting in an application of total incident energy on the imaging layer of about 0.5 foot-candle seconds. The receiver sheet is then peeled from the set with the potential source still connected. The small amount of Sohio present evaporates after separation of the sheets yielding a pair of excellent quality images with a polymer overcoated positive image adhering to the donor sheet and a negative image adhering to the receiver sheet. The donor sheet is then placed on a Travelgraph Projector made by Projection Optics Co., Inc., and the image projected onto a white surface. The projected image appears to be dark brown or black. The image is then buffed to smooth the surface of the imaging layer by slightly rubbing the image to 15 strokes with a cotton glove. The image is again projected. The image is now found to project a medium blue color.

EXAMPLE II PRIOR ART The experiment of Example I is repeated with the exception that the activator solution consists of Sohio 3440 only. Upon separation of the donor and receiver sheets the Sohio evaporates yielding a pair of excellent quality images with a positive image adhering to the donor sheet and a negative image adhering to the receiver sheet. The image is then projected as in Example I. The image projects a very dark brown or black color. The donor sheet is then buffed as in Example I. It is found that buffing as in Example I damages the image by scratching and on projection only a slight improvement in color is obtained.

EXAMPLE III An activator solution is prepared by dissolving enough Piccotex 120 (a styrene-vinyl toluene copolymer available from the Pennsylvania Industrial Chemical Company) in 500 cc. of Sohio 3440 to form a 5 percent solution.

Approximately 3 grams of Naphthol Red B S-nitro-oanisidine 3-hydroxy-3'-nitro Z-naphthanilide C. I. No. 12355 is pre-milled with 60 ml of DC Naphtha 2032 in a glassjar as in Example I.

A binder solution prepared as in Example I is then added to the Naphthol Red B-naphtha mixture as in Example l. The materials are then heated to a temperature of 65C for about two hours and then are cooled to room temperature. About 60 ml of isopropanol is then added to the mixture and the mixture is milled as in Example I for about 30 minutes.

The paste-like mixture is then coated on 3 mil Mylar as in Example I. The imaging layer is then activated with the activator of this Example and exposed to imagewise activation and to field as in Example I except that imagewise exposure is adjusted to about 2 foot-candles. Imagewise exposure is continued for about 15 seconds resulting in application of about 30 foot-candle seconds on the imaging layer. Upon separation of the receiver and donor sheet a pair of excellent quality images are produced with a polymer overcoated positive image adhering to the donor sheet and a negative image adhering to the receiver sheet. The donor sheet is then used as a transparency as in Example I. The projected image appears dark brown or black. The

donor sheet is then buffed as in Example I. The image is now found to project a true medium red.

EXAMPLE IV PRIOR ART The experiment of Example III is repeated except that the imaging layer is activated with activator solution consisting of Sohio 3440 only. Upon separation of the donor and receiver sheets, the Sohio evaporates yielding a pair of excellent quality images with a positive image adhering to the donor sheet and a negative image adhering to the receiver sheet. The image is then projected as in Example III. The image projects a dark brown or black color. The donor sheet is then buffed as in Example I. It is found that buffing as in Example I damages the image by scratching and on projection only a slight improvement in color is obtained.

EXAMPLE V An activator solution is prepared by dissolving enough Aroclor 5442 (a chlorinated polyphenyl available from Monsanto Chemical Company, St. Louis, M0.) in 500 cc of Sohio 3440 to form a l0 percent solution.

Approximately l .5 grams of the .1: form of phthalocyanine prepared as in Example I and approximately 1.5 grams of purified Benzidene Yellow available as Ben; Yellow 30-0535 from Hilton Davis of Cincinnati, Ohio. The Benzidene Yellow is purified as follows Approximately 100 grams Qf'thC Benzidene Yellow is slurried in 1,500 ml of a mixture of 50% isopropanol and 50 percent Sohio 3440. The slurry is heated to C and stirred for A hour. The mixture is then filtered and washed with isopropanol, then allowed to dry.

The mixture of pigments is then pre-milled as in Example I. A binder solution prepared as in Example I is then added to the pre-milled pigments as in Example I. The materials are then heated to a temperature of 65C for about 2 hours and then are cooled to room temperature. About 60 ml of isopropanol is then added to the mixture and the mixture is milled as in Example I for about 30 minutes.

The paste-like mixture is then coated on 3 mil Mylar as in Example I. The imaging layer is then activated with the activator of this Example and exposed to imagewise light and to field as in Example I. Upon separation of the receiver and donor sheet, the Sohio evaporates yielding a pair of excellent quality images with a polymer overcoated positive image adhering to the donor sheet and a negative image adhering to the receiver sheet. The donor is then used as a transparency as in Example I. The projected image appears dark brown or black. The donor sheet is then buffed as in Example I. The projected image is now found to be a true medium green.

EXAMPLE VI PRIOR ART The experiment of Example V is repeated except that the imaging layer is activated with an activator solution consisting of Sohio 3440 only. Upon separation of the donor and receiver sheets the Sohio evaporates providing a pair of excellent quality images with a positive image adhering to the donor sheet and a negative image adhering to the receiver sheet. The image is then projected as in Example I. The projected image appears dark brown or black. It is found that buffing as in Example I damages the image by scratching and on projection only a slight improvement in color is obtained.

EXAMPLE VII An activator solution is prepared by dissolving enough Aroclor 5442 (a chlorinated polyphenyl available from Monsanto Chemical Co., St. Louis, M0.) in 500 cc of Sohio 3440 to form a percent solution.

Approximately 2.5 grams of x form phthalocyanine prepared as in Example I, approximately 2.8 grams of purified Irgazin Red available as lrgazin Red-ZBLT as described in U. S. Patent No. 2,973,358 available from Geigy Chemical Co., Ardsley, N.Y. and approximately 1.2 grams of purified lrgazin Yellow available as lrgazin Yellow 2GLT also described in US. Pat. No. 2,973,358 are pre-milled as in Example I.

The lrgazin Red and lrgazin Yellow are previously purified in the same manner as the Benzidene Yellow pigment of Example V.

TA binder solution made as in Example I is then added to the pre-milled pigments as in Example I. The materials are then heated to a temperature of 65C for about 2 hours and then are cooled to room temperature. About 60 ml of isopropanol is then added to the mixture and the mixture is milled as in Example I for 30 minutes. a

The paste-like mixture is then coated on 3 mil Mylar as in Example I. The imaging layer is activated with the activator of this Example and exposed to imagewise light and to field as in Example I.

Upon separation of the receiver and donor sheet, the Sohio evaporated yielding a pair of excellent quality images with a polymer overcoated positive image adhering to the donor sheet and a negative image adhering to the receiver sheet. The donor is then used as a transparency as in Example I. The projected image appears black. Buffing as in Example I produces no change.

EXAMPLE VIII PRIOR ART The experiment of Example VII is repeated except that the activator solution comprises Sohio 3440 only. The donor side image produced as in Example VII is found to be scratched when buffed as in Example I.

EXAMPLE IX A binder solution is prepared by mixing together in a melt solution about 45 grams of purified polyethylene DYLT, about 22.5 grams of Paraflint RG, about 7.5 grams of purified Elvax 420, about 1.5 grams of purified polyethylene DYDT, a polyethylene available from Union Carbide Co., about 37.5 grams of Piccotex 100, a styrene-vinyl toluene copolymer available from Pennsylvania Industrial Chemical Co. and about 300 ml. of clay bed purified Sohio 3440 Solvent. The mixture is heated with stirring until a water-clear solution is obtained. The solution is allowed to cool to room temperature thus forming a white paste. A mixture of pigments is prepared by placing in a jar mill about 37.5 grams of phthalocyanine as obtained in Example I, about 18 grams of purified Algol Yellow, about 42 grams of purified lrgazin Red and about 900 ml of clay bed purified DC Naphtha which mixture is milled for four hours at a jar speed of 60 rpm using 50 percent by volume flint stones inch to inch in diameter which have previously been rinsed 6 times with deonized water followed by acetone rinse and air drying. The cold binder paste is added to the pre-milled pigment in the jar mill and the mixture is milled for an additional 16 hours after which the jar is heated in a water bath at 65C. After cooling to room temperature, about 1 liter of reagent grade isopropol alcohol is added to the jar and the pigment/binder mixture is milled for 20 minutes.

The thus prepared imaging material is coated evenly onto a 3 ml thick Nylar sheet which is 10 inches wide and about 300 feet long by means of dip coating and doctoring with a wire wound rod to provide a dry coating weight of 0.25 g./ft. After the evaporation of the coating solvent, the coated mylar sheet is cut into convenient size for use as a donor in an imaging procedure.

An activator is prepared by mixing together in equal weight amounts a low melting hydrocarbon wax available under the tradename Sohio Parowax (melting point 35-56C) and a modified styrene polymer available under the tradename Piccolastic A-50 from the Pennsylvania Industrial Chemical Co. The mixture is heated to about 90C with stirring and then coated on a sheet of aluminum foil by means of a No. 10 wire wound drawdown rod while the aluminum foil is maintained at about C which results in a layer about 15 microns in thickness on the aluminum. After cooling, the aluminum foil is placed in an imaging position on a heated platen which raises the temperature of the coating to about 70C thereby melting the wax and, while heated, the imaging layer of the donor prepared as described above is placed in contact with the activator layer on the aluminum foil. A corona discharge device connected to the positive terminal of a 5.2 KV direct current power supply, is passed over the Mylar sheet while the aluminum foil is connected to the negative terminal of the power supply. The thus charged Mylar is imagewise exposed by means of a commercial Omega photographic enlarger for 5 seconds at a setting of fl 6. After exposure, the Mylar sheet is separated from the aluminum sheet whereby the imaging layer fractures in imagewise configuration leaving a positive image on the donor sheet and a negative image on the aluminum foil receiver. Upon cooling the images are plastic coated and well fixed to their respective substrates.

Although specific components and proportions have been stated in the above description of preferred embodiments of the invention, other typical materials as listed above if suitable may be used with similar results. In addition, other materials may be added to the mixture to synergize, enhance or otherwise modify the properties of the imaging layer. For example, various dyes, spectral sensitizers or electrical sensitizers such as Lewis acids may be added to the several layers.

Other modifications and ramifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure. These are intended to be included within the scope of this invention.

What is claimed is:

1. A method ofimaging comprising:

a. providing an electrically photosensitive imaging layer sandwiched between a donor sheet and a receiver sheet, at least one of said donor and receiver sheets being at least partially transparent to electromagnetic radiation to which said layer is sensitive;

. rendering said imaging layer structurally fracturable in response to the combined effects of an applied electrical field and exposure to electromag netic radiation, to which said layer is sensitive, by applying to said layer an activator, comprising at least one plastic component held in a liquid medium, said medium being selected from the group consisting of solvents, partial solvents, swelling and softening agents for said layer;

c. maintaining an electric field across said imaging layer;

d. exposing said imaging layer to a pattern of activating electromagnetic radiation;

e. separating said receiver sheet from said donor sheet while under said electric field whereby said imaging layer fractures in imagewise configuration forming a plastic overcoated image on at least one of said donor and receiver sheets and f. buffing said coated image whereby a projectable image in true color is obtained.

2. The method of claim 1 wherein said activator comprises a plastic component dissolved in a solvent component, said solvent component comprising at least a partial solvent for said imaging layer.

3. The method of claim 1 wherein said activator comprises a plastic component suspended in a solvent component said solvent component comprising at least a partial solvent for said imaging layer.

4. The method of claim 1 wherein said activator is a thermo-solvent in solid form having a melting temperature lower than said imaging layer and including the additional step of melting said activator.

5. The method of claim 1 wherein said activator comprises styrene-vinyl toluene copolymer dissolved in kerosene.

6. The method of claim 1 wherein said activator comprises chlorinated polyphenyl dissolved in kerosene.

7. The method of claim 1 wherein said imaging layer comprises metal-free phthalocyanine in a binder.

8. The method of claim 1 wherein said imaging layer comprises metal-free phthalocyanine in the X crystalline form in a binder.

9. The method of claim 1 wherein said imaging layer comprises a mixture of electrically photosensitive pigments in a binder.

10. The method of claim 4 wherein the thermo-solvent comprises a low melting wax.

11. The method of claim 4 wherein the plastic component is soluble in said activator.

12. The method of claim 1 wherein the activator is a thermo-solvent having a melting temperature lower than said imaging layer and the plastic component is insoluble in said activator.

3. The method of claim 4 wherein the thermo-solvent is a low melting wax. 

2. The method of claim 1 wherein said activator comprises a plastic component dissolved in a solvent component, said solvent component comprising at least a partial solvent for said imaging layer.
 3. The method of claim 1 wherein said activator comprises a plastic component suspended in a solvent component said solvent component comprising at least a partial solvent for said imaging layer.
 4. The method of claim 1 wherein said activator is a thermo-solvent in solid form having a melting temperature lower than said imaging layer and including the additional step of melting said activator.
 5. The method of claim 1 wherein said activator comprises styrene-vinyl toluene copolymer dissolved in kerosene.
 6. The method of claim 1 wherein said activator comprises chlorinated polyphenyl dissolved in kerosene.
 7. The method of claim 1 wherein said imaging layer comprises metal-free phthalocyanine in a binder.
 8. The method of claim 1 wherein said imaging layer comprises metal-free phthalocyanine in the X crystalline form in a binder.
 9. The method of claim 1 wherein said imaging layer comprises a mixture of electrically photosensitive pigments in a binder.
 10. The method of claim 4 wherein the thermo-solvent comprises a low melting wax.
 11. The method of claim 4 wherein the plastic component is soluble in said activator.
 12. The method of claim 1 wherein the activator is a thermo-solvent having a melting temperature lower than said imaging layer and the plastic component is insoluble in said activator.
 13. The method of claim 4 wherein the thermo-solvent is a low melting wax. 